?-Aq%',3  c^6^ 


1 


Connecticut  Agricultural 
Experiment  Station 

NEW  HAVEN,  CONN. 
BULLETIN  208  OCTOBER,  1918 

ENTOMOLOGICAL  SERIES  No.  26. 


S 
■     ^3 


Insects  Attacking  the  Potato  Crop 
in  Connecticut 


By  W.  E    BRITTON. 


CONTENTS 


Page 

Officers  and  Staff  of  Station 102 

Insects  Attacking  the  Potato 103 

Chewing  Insects 103 

Potato  Flea  Beetle 103 

Colorado  Potato  Beetle 106 

Three-Lined  Potato  Beetle 109 

Tortoise  Beetles 110 

The  Blister  Beetles 110 


Page 

The  Stalk  Borer Ill 

Cutworms 112 

Wireworms 113 

White  Grubs 114 

Sucking  Insects 115 

The  Potato  Aphid 115 

The  Four-Lined   Leaf-Bug 118 

Summary 119 


The  Bulletins  of  this  Station  are  mailed  free  to  citizens  of  Connecti- 
cut who  apply  for  them,  and  to  others  as  far  as  the  editions  permit. 


CONNECTICUT  AGRICULTURAL  EXPERIMENT  STATION 

OFFICERS  AND  STAFF 


BOARD  OF  CONTROL. 
His  Excellency,  Marcus  H.  Holcomb,  ex-officio,  President. 

James  H.  Webb,  Vice  President Hamdcn 

George  A.  Hopson,  Secretary Wallingford 

E.  H.  Jenkins,  Director  and  Treasurer New  Haven 

Joseph  W.  Alsop . Avon 

Wilson  H.  Lee Orange 

Elijah  Rogers Southington 

William  H.  Hall South  Willington 


Administration. 


Chemistry, 

Analytical  Laboratory, 


Protein  Research. 


Botany. 


Entomology. 


Forestry. 


Plant  Breeding 


Vegetable  Growing. 


E.  H.  Jenkins,  Ph.D.,  Director  and  Treasurer. 

Miss  V.  E.  Cole,  Librarian  and  Stenographer. 

Miss  L.  M.  Brautlecht,  Bookkeeper  and  Stenographer. 

William  Veitch,  In  charge  of  Buildings  and  Grounds. 


*JoHN  Phillips  Stbeet,  M.S. 

E.  Monroe  Bailey,  Ph.D.,  Chemist  in  charge. 

*C.  B.  MoRisoN,  B.S.,  C.  E.  Shepard,    1 

M.  d'Esopo,  Ph.B.  I  ^^^i^t<^nts. 

V.  L.  Churchill,  Sampling  Agent. 

T.  B.  Osborne,  Ph.D.,  D.Sc,  Chemist  in  Charge. 
Miss  E.  L.  Ferry,  M.S.,  As 


G.  P.  Clinton,  Sc.D.,  Botanist. 

E.  M.  STODD.4.RD,  B.S.,  Assistant  Botanist. 

Florence  A.   McCormick,  Ph.D.,  Scientific  Assistant. 

G.  E.  Graham,  General  Assistant. 

W.  E.  Britton,  Ph.D.,  Entomologist;   State  Entomologist. 

B.  H.  Walden,  B.Agr.,  First  Assistant. 

M.  p.  Zappe,  B.S.,  *I.  W.  Davis,  B.Sc,  Assistants. 
Miss  Martha  de  Bussy,  Stenographer. 

Walter  O.  Filley,  Forester;   also  State  Forester 

and  State  Forest  Fire  Warden. 
A.  E.  Moss,  M.F.,  Assistant  State  and  Station  ForeHer. 
Miss  E.  L.  Avery,  Stenographer. 

Donald  F.  Jones,  Sc.D.,  Plant  Breeder. 

C.  D.  HuBBELL,  Assistant. 

W.  C.  Pelton,  B.S. 


*  Absent  on  leave.     In  service  of  the  United  States. 


Insects  Attacking  the  Potato  Crop  in 
Connecticut. 

By  W.  E.  Britton,  State  and  Station  Entomologist. 


As  a  rule  potatoes  in  Connecticut  are  not  greatly  injured  by  in- 
sects, and  remedial  measures  are  seldom  required  other  than  to 
apply  lead  arsenate  to  control  the  Colorado  beetle. 

In  certain  seasons,  however,  other  chewing  insects  will  cause 
some  damage.  Thus  in  1918  the  potato  ilea  beetle  was  abundant 
throughout  the  state  and  perforated  the  leaves,  considerably  weak- 
ening the  plants  and  injuring  the  crops.  Also  the  three-lined 
potato  beetle  and  one  of  the  tortoise  beetles  were  common  and  of 
course  did  some  damage. 

Cutworms,  wireworms,  blister  beetles,  white  grubs  and  the  stalk 
borer  all  take  an  occasional  toll  from  the  harvest  of  the  farmer. 
Then  in  some  localities  in  certain  seasons  sucking  insects,  especially 
aphids,  may  attack  and  seriously  injure  the  crop  as  was  the  case  in 
1917  and  1918. 

The  object  of  this  bulletin  is  to  bring  togetlier  in  a  form  con- 
venient for  ready  reference,  brief  descriptions  and  illustrations  of 
both  the  common  and  the  uncommon  insect  pests  of  the  potato  in 
Connecticut  and  to  recoonmend  control  measures,  so  that  the  grower 
may  have  a  guide  which  may  be  safely  followed.  Most  of  the  in- 
sects mentioned,  will  readily  be  recognized  by  comparing  with  the 
accompanying  illustrations  (plates  XIII-XX)  which  are  essentially 
a  part  of  this  bulletin. 

CHEWING  INSECTS. 

All  pests  grouped  under  this  heading  gnaw  away  parts  of  the 
plant,  and  those  which  feed  upon  the  leaves  can  usually  be  con- 
trolled by  arsenical  poisons. 

Potato  Flea  Beetle. 
Epitrix  cucumeris  Harris. 
This  is  a  small,  black,  jumping  beetle  about  one-sixteenth  of  an 
inch  in  length.    The  antennae  and  legs  are  yellowish,  but  the  head 


104  CONNECTICUT   EXPERIMENT   STATION    BULLETIN    208. 

thorax  and  wing-covers  are  jet  black.  There  is  a  deep  transverse 
groove  at  the  base  of  the  thorax,  and  the  wing  covers  are  micro- 
scopically pitted  lengthwise  in  rows,  and  bear  minute  gray  hairs. 
(See  figure  1.)  Other  species  injure  the  potato  in  the  Southern 
and  Western  states,  but  in  Connecticut,  the  attacks  observed  were 
due  to  U.  cucumeris  sometimes  called  the  cucumber  flea-beetle, 
though  it  more  commonly  injures  the  potato.  It  is  usually  the  first 
insect  to  attack  the  potato  vines  as  soon  as  they  come  up.  The 
beetles  jump  quickly  when  disturbed  aiid  eat  small  holes  from  the 
under  side  of  the  leaves,  soon  perforating  them.  In  many  cases 
the  feeding  does  not  extend  through  the  leaf  but  appears  as  a 
blister-like  injury  on  the  lower  surface.  Flea-beetle  injury  is 
shown  on  plate  XIII,  a. 


Figure  1.  The  cucumber  flea  beetle  Epitrix  cucumeris,  greatly  en- 
larged. ■  (After  Chittenden,  Bureau  of  Entomology,  U.  S.  Department 
of  Agriculture.) 

The  beetles  hibernate  under  rubbish  and  leaves,  and  the  eggs 
are  laid  in  May  or  June.  The  larvae  are  slender  thread-like  white 
worms,  which  live,  and  transform  in  the  ground,  feeding  upon  the 
roots  and  tubers.  Many  tubers  from  the  writer's  garden  where  the 
flea-beetles  were  very  abundant,  had  small  pin-holes  extending  in- 
ward from  the  surface  sometimes  as  far  as  half  an  inch,  where  the 
slender  larvae  had  mined,  causing  imperfect  or  "pimply"  potatoes. 
The  potato  flea-beetle  has  not  been  carefully  studied  in  Connecticut 
but  it  is  generally  considered  that  there  are  two  and  perhaps  three 
generations  each  year. 

Control  Measures:  Flea-beetles  may  be  killed  by  arsenical 
poisons,  trapped  by  mechanical  devices,  or  driven  away  by  repel- 
lents. 

Thoroughly  coating  both  upper  and  under  surfaces  of  the  leaves 
with  a  heavy  spray  of  lead  arsenate  (1  lb.  in  5  gallons  water)  will 


INSECTS  ATTACKING  POTATOES.  105 

usuall}^  prevent  injury.  In  some  experiments  a  few  years  ago, 
tomato  and  tobacco  plants  were  dipped  in  this  poison  before  being 
set  in  the  field,  and  these  plants  were,  not  injured  though  un- 
treated plants  close  by  were  badly  eaten. 

When  abundant  as  in  1918,  the  absolute  control  of  this  insect  is 
difficult  and  not  wholly  successful.  Several  growers  reported  that 
they  had  sprayed  as  carefully  and  as  thoroughly  as  seemed  possible, 
yet  there  were  just  as  many  beetles  as  ever.  Be  that  as  it  may  the 
beetles  are  difiicult  to  control  by  poisoning,  because  they  jump 
about  and  feed  but  little  in  one  place.  In  the  ordinary  spraying 
operations,  there  are  plenty  of  places  where  the  leaves  are  not  cov- 
ered with  poison,  and  in  such  places  the  flea-beetles  can  feed  un- 
harmed. For  under-spraying  it  is  necessary  to  use  extension  rods 
bent  at  an  angle  of  about  forty-five  degrees  near  the  nozzle. 

Bordeaux  Mixture  is  often  recommended  as  a  remedy  for  flea- 
beetles;  it  is  only  a  repellant,  however,  and  does  not  kill  then-u 
Wherever  Bordeaux  Mixture  is  used  to  prevent  blight,  this  mixture 
containing  lead  arsenate  can  and  should  be  applied  to  check  flea- 
beetles  rather  than  to  prepare  a  different  mixture. 

On  account  of  their  jumping  habits,  flea-beetles  may  be  caught 
in  "tanglefoot"  or  other  sticky  materials  and  thus  be  greatly  re- 
duced in  numbers.  A  few  years  ago  Professor  C.  L.  Metcalf  of  the 
Ohio  State  University,  devised  and  used  an  apparatus  which  has 
since  been  described.*  Briefly,  his  device  consisted  of  a  soap  box 
with  cover,  the  front  end  removed,  nearly  half  of  the  central  part 
cf  the  bottom  and  a  good-'sized  notch  in  the  lower  side  of  the  rear 
end  cut  away.  The  inside  of  this  box  was  coated  with  "^tangle- 
foot" and  when  it  was  pushed  forward  along  the  row  the  flea-bee- 
tles on  jumping  when  disturbed  were  caught  in  the  sticlcy  material. 
Modifications  were  suggested,  and  wires  were  introduced  to  keep  the 
foliage  from  contract  with  the  "tanglefoot."  The  box  was  mounted 
on  wheels  so  that  one  man  could  manipulate  it,  and  it  caught  flea- 
beetles  at  the  rate  of  over  25,000  per  acre,  most  of  them  being 
stuck  on  the  lower  ledges  of  the  box.  Professor  Metcalf  suggests 
the  possibilit}''  of  using  trays  containing  kerosene  or  a  heavier  oil  in 
the  place  of  these  ledges,  because  the  trays  could  easily  be  emptied. 
It  was  necessary  to  stop  occasionally  and  remove  the  beetles  and 
apply  more  "tanglefoot." 


Journal  of  Economic  Entomology,  Vol.  8,  p.  240,  1915. 


106  CONNECTICUT   EXPERIMENT   STATION    BULLETIN    208. 

Possibly  some  device  of  this  sort  may  solve  the  prohlein  of  con- 
trolling flea-beetles,  in  seasons  when  they  are  unusually  alnindant, 
and  when  the  success  of  spraying  is  questionable. 

Colorado  Potato  Beetle. 

Leptinotarsa  (Doryphora)  decemlineata  Say. 

For  many  years  this  insect  has  been  regarded  as  the  chief  insect 

enemy  of  the  potato  crop,  and  it  more  than  any  other  single  species 

is  responsible  for  the  development  of  the  use  of  arsenical  poisons — 

J-'aris  green  for  many  years  being  the  only  poison  used. 

The  Colorado  beetle  is  a  native  of  the  Eocky  Mountain  region 
of  the  Southwest,  where  it  fed  upon  the  indigenous  plants  of  the 


I 


Figure  2.     Colorado  potato  beetle;  larva  and  adult.  Natural  size. 

potato  family.  As  the  country  gradually  became  settled,  and  eacti 
pioneer  pushed  westward  a  little  beyond  his  neighbor  and  planted 
his  patch  of  potatoes,  there  came  a  time  about  1855  when  the 
frontier  of  potato  growing  reached  the  region  where  these  beetles 
were  native,  and  they  began  to  feed  upon  the  potato  foliage.  These 
potato  patches  like  rungs  of  a  ladder  made  excellent  stepping  places 
in  the  eastward  progress  of  the  beetle.  About  1864  it  crossed  the 
Mississippi  Eiver  and  in  about  1874  it  was  first  recorded  along  the 
Atlantic  seaboard.  At  first,  hand-gathering  was  the  remedy  and  it 
was  predicted  that  farmers  must  give  up  growing  potatoes.  Soon 
it  was  found  that  Paris  green  would  save  the  vines  and  kill  the 
insects.  Thus  for  nearly  fifty  years,  potatoes  have  been  grown  and 
the  Colorado  beetle  held  in  check  by  the  use  of  arsenical  poisons. 


INSECTS  ATTACKING  POTATOES.  107 

The  eggs  are  bright  yellow  and  are  laid  on  the  under  side  of  the 
leaves  in  clusters  of  about  a  dozen  as  shown  on  plate  XIV,  b, 
and  hatch  in  about  a  week.  One  female  lay  from  500  to  1,000 
eggs.  The  adult  is  a  yellow  beetle  about  three-eighths  of  an  inch 
long,  with  five  black  stripes  running  lengthwise  on  each  wing- 
cover  and  a  series  of  black  spots  on  the  thorax.  The  larva  is  a 
stout,  fleshy  grub  reddish  in  color  with  black  head  and  marked 
with  black  spots  as  shown  on  plate  XIY,  a.  Both  adult  and  larvae 
are  shown  in  figure  2. 

The  adults  appear  in  early  spring  and  are  ready  to  feed  upon  the 
first  potato  leaves  to  show  above  ground.  The  larvae  require  about 
three  weeks  to  reach  maturity  when  they  go  into  the  ground  to 
pupate.  Probaibly  there  are  two  and  sometimes  three  generations 
each  year,  the  i^dnter  being  passed  in  the  ground  as  pupae  or  as 
adults. 

Perhaps  the  most  important  insect  parasites  of  the  Colorado 
potato  beetle  in  Connecticut  are  the  two-winged  flies  belonging  to 
the  family  Tachinidae.  Two  species  have  been  reared  from  larvae 
and  identified  as  D oryplioropliaga  dorypliorae  Eiley,  and  D.  aher- 
rans  Town. 

Several  predaceous  insects  feed  upon  the  eggs  or  larvae  of  the 
Colorado  beetle;  among  these  are  the  lady  beetles  Vhich  devour  the 
eggs  and  small  lar^'ae,  the  ground  beetles  especially  Lehia  grandis 
Hentz,  and  the  soldier  bugs,  particularly  the  spined  soldier  bug, 
Podisus  macuUventriis  Say. 

Turkeys,  crows,  and  red-breasted  grossbeaks  feed  somewhat  on 
the  Colorado  potato  beetle. 

Control  Measures:  Spraying  the  foliage  Avith  an  arsenical 
poison  is  the  most  satisfactory  means  of  control  in  the  field.  For 
nearly  fifty  years  Paris  green  was  used  for  this  purpose,  but  it  has 
now  been  superseded  nearly  everywhere  by  lead  arsenate. 

Arsenate  of  lead  is  safer  than  Paris  green  and  adheres  better  to 
the  foliage.  It  contains  less  arsenic  and  therefore  requires  more 
per  barrel  to  kill  the  beetles.  It  is  made  in  both  the  dry  or  pow- 
dered form,  and  in  form  of  paste  containing  50  per  cent,  water. 
Usually  it  is  applied  as  follows : 

Lead  arsenate    (paste) 3  lbs. 

Water    50  gals. 


108  CONNECTICUT   EXPERIMENT   STATION   BULLETIN   208. 

Instead  of  the  paste,  the  dry  form  may  be  substituted  using  half 
as  much  by  weight  or  one  and  one-half  pounds.  It  may  also  be 
sifted  or  blown  upon  the  wet  plants  without  being  mixed  with 
lime  or  any  other  diluent.  This  poison  may  also  be  added  to  Bor- 
deaux Mixture  or  nicotine  solution  without  injury  to  the  foliage 
providing  soap  is  omitted. 

Paris  green  is  a  powerful  poison  in  the  form  of  a  dry  powder. 
It  may  be  mixed  at  the  rate  of  1  lb,  in  100  lbs.  with  land  plaster 
or  air-slaked  lime  and  dusted  or  blown  upon  the  wet  plants  or  ap- 
plied as  a  spray  using  from  one- third  to  one-half  pound  in  50  gal- 
lons of  water.  As  Paris  green  contains  some  free  arsenic  in  acid 
form  there  is  always  danger  of  burning  the  leaves  with  it  unless  lime 
is  added  to  take  care  of  the  free  acid.  A  good  formula  for  making 
the  spray  is  as  f ollows : 

Paris  green   ^  lb. 

Quick  lime   2  lbs. 

Water 50  gals. 

The  lime  should  be  slaked  before  adding  to  the  mixture.  The 
poison  may  be  used  in  combination  with  Bordeaux  Mixture  with- 
out additional  lime  as  the  Bordeaux  Mixture  contains  an  excess  of 
lime.  Though  Piaris  green  may  be  used  successfully,  as  it  has  been 
used  for  many  years,  it  will  wash  off  vnth  the  first  heavy  rain  unless 
Bordeaux  Mixture  or  some  other  good  adhering  agent  is  present. 

During  the  past  few  years,  several  arsenical  poisons  have  been 
tested  in  the  field,  and  some  even  have  been  placed  upon  the  mar- 
ket. Arsenite  of  zinc  is  one  of  these  tested  in  Connecticut  a  few 
years  ago.  Arsenate  of  lime  is  a  more  recent  acquisition,  which  is 
made  in  dry  or  powder  form.  It  is  very  fine  and  light,  and  remains 
well  in  susjoension.  It  was  considerably  cheaper  in  1918  than  lead 
arsenate.  When  used  there  should  be  an  excess  of  lime  present  to 
prevent  burning.  A  spray  mixture  containing  Bordeaux  already 
has  lime  in  excess,  so  that  additional  lime  is  unnecessary.  In  the 
small  home  garden,  the  beetles  may  be  gathered  by  hand  and  de- 
stroyed, especially  where  on  account  of  children  or  domestic  ani- 
mals it  seems  undesirable  to  use  poison. 

.   As  a  rule  the  adult  beetles  emerge  from  the  ground  early  in  May 

and  attack  some  of  the  potatoes  as  soon  as  the  plants  appear.    Later 

the  larvae  also  appear  on  certain  plants  here  and  there  scattered 

■  over  the  field.    At  this  time  of  the  season  lead  arsenate  is  about  the 


INSECTS  ATTACKING  POTATOES.  109 

only  spray  material  required.  The  plants  are  small  and  if  a  power 
sprayer  is  used  most  of  the  material  will  strike  the  ground  and 
consequently  be  wasted. 

Probably  the  most  economical  treatment  is  to  send  a  man  through 
the  field  with  a  compressed,  air  sprayer  (or  with  duster  or  powder 
gun  if  the  dry  poison  is  used)  and  poison  only  those  plants  where 
the  insects  are  feeding.  Later  when  the  larvae  are  more  abundant 
and  most  of  the  plants  are  being  injured,  all  should  be  sprayed. 

As  the  blight  does  not  start  until  about  July  1st,  Bordeaux  Mix- 
ture may  be- withheld  until  the  latter  part  of  June:  then  the  foliage 
should  be  kept  covered  as  long  as  the  plants  are  making  growth  and 
lead  arsenate  should  be  added  to  the  Bordeaux  as  long  as  there  is 
danger  from  leaf -eating  insects. 

The  traction  power  sprayers  often  used  in  potato  fields  are  gen- 
erally unsatisfactory  (1)  because  they  do  not  apply  enough  liquid 
(2)  because  they  treat  all  plants  alike  whether  infested  or  not.  If 
an  outfit  is  used  which  does  not  depend  upon  traction  for  power,  it 
is  possible  to  stop  and  spray  for  a  few  minutes,  in  order  to  thor- 
oughly coat  the  plants  in  certain  sections  of  the  field  where  the 
infestation  is  heaviest. 

A  gasoline  engine  will  furnish  power  for  larger  operations,  and 
a  hand  pump  like  that  shown  on  plate  XIII,  b,  will  answer  nicely 
for  small  fields. 

Theee-Lined  Potato  Beetle. 
Lema  trilineata  Oliv. 

This  beetle  is  yellow  vath  three  black  stripes  running  lengthwise 
and  resembles  the  striped  cucumber  beetle  but  is  larger,  and  the 
thorax  is  constricted  and  marked  with  two  black  dots.  The  eggs  are 
yellow  and  resemble  those  of  the  Colorado  beetle,  but  are  smaller 
and  are  more  apt  to  be  attached  to  the  midrib  of  the  leaf  instead  of 
promiscuously  in  clusters.  They  are  shown  on  plate  XY,  a.  Both 
kinds  are  laid  on  the  under  side  one  end  of  each  egg  being  attached 
to  the  leaf. 

The  larvae  usually  line  up  in  a  row  side  by  side  on  the  under 
surface  and  devour  the  leaf  working  from  the  tip  toward  the  base 
and  leaving  the  larger  veins.  The  larvae  are  buff  or  tan  in  color, 
but  are  partly  covered  by  their  ot\ti  black  or  broTsra  excrement,  giv- 
ing them  a  very  disgusting  appearance.  Eggs,  adults  and  larvae 
are  shown  on  plate  XV. 


110  CONNECTICUT   EXPERIMENT   STATION    BULLETIN    208. 

There  are  two  generations  each  year,  the  larvae  appearing  in 
June  a-nd  in  August,  and  the  winter  is  passed  in  the  pupa  stage. 
This  insect  was  more  abundant  in  1918  than  the  writer  has  ever 
seen  it  in  Connecticut.  The  same  arsenical  poison  that  is  used 
against  the  Colorado  beetle,  will  control  the  three-lined  beetle. 

Tortoise  Beetles. 

Occasionally  potatoes  are  attacked  by  small  hemispherical  beetles 
having  a  rather  conspicuous  marginal  flange,  Imown  as  tortoise  bee- 
tles. They  feed  upon  the  wild  morning  glory  or  bindweed  and  also 
upon  the  sweet  potato.  There  are  at  least  three  species  in  Connecti- 
cut belonging  to  the  genus  Coptomjcla.  Coptocycla  licolor  is  of  a 
beautiful  irridescent  gold  color  in  life  often  with  inconspicuous 
black  spots.  It  is  sometimes  called  the/'gold  bug"  or  "gold  beetle." 
'J'he  other  two  species  C.  clavata  Fahv  and  C.  guttata  Oliv  are  both 
brown  on  the  back  with  the  marginal  flange  translucent.  In  C.  gut- 
tata the  dark  portion  is  more  or  less  translucent  spotted.  C. 
iclavata  is  larger  with  the  brown  area  very  rough.  This  species  is 
sshown  on  plate  XVI,  a,  and  was  quite  prevalent  in  Connecticut  in 
:1918,  being  observed  in  Kew  Haven  and  Mount  Carmel  and  was 
Teceived  from  Clinton,  Guilford,  Meriden,  Monroe,  Plainville,  and 
Shelton. 

The  eggs  are  laid  singly  on  the  veins  or  stems  of  the  leaves,  each 
egg  being  cO'Vered  with  a  small  mass  of  black  excrement.  The  lar- 
vae are  dull  green,  oval,  flattened,  with  lateral  projections  or  spines, 
and  feed  upon  the  under  surface  of  the  leaves.  They  carry  their 
excrement  on  the  caudal  spines.  There  is  only  one  generation  each 
season  and  the  winter  is  passed  in  the  adult  stage,  the  beetles  hiding 
in  crevices  and  appearing  on  the  potato  plants  during  the  month  of 
May. 

Though  this  beetle  feeds  upon  the  potato  leaves,  it  probably  does 
not  cause  very  great  da.m'age,  and  may  readily  be  controlled  by  the 
arsenical  poisons. 

The  Blister  Beetles. 

There  are  several  species  of  blister  beetles  w'hich  may  be  found 
feeding  upon  the  potato  in  Connecticut.  These  are  about  half  an 
inch  long,  less  than  half  as  broad,  and  vrith  soft  wing  covers.  They 
fed  upon  potatoes  long  before  the  advent  of  the  Colorado  beetle  and 
are  some  times  called  "old-fashioned  potato  beetles."    Their  attacks 


PLATE  XIII, 


a.      Potatoleaves  injured  by  Potato  Flea  Beetle,  considerably  reduced. 


b.     A  good  hand-power  spray  outfit  for  a  potato  field  of  two  or  three 

acres  or  less. 


PLATE  XIV. 


a.     Larvae  nearly  full  grown  feeding  upon  leaves.      Natural  size. 


b.     Eggs,  twice  natural  size. 
COLORADO  POTATO  BEETLE, 


PLATE   XV. 


a.     Larvae  feeding  upon  leaf,  natural  size. 


b.      Cluster    of    eggs, 
natural  size. 


c.     Adults  on  leaf,  natural  size. 
THREE-LINED  POTATO  BEETLE. 


PLATE  XVI. 


a.     Clavate  Tortoise  Beetle,  adults  on  leaf,  natural  size. 


b.     Margined  Blister  Beetle,  adults  feeding  on  leaves,  natural  size. 


PLATE  XVII. 


a.     Potato  tubers  injured  by  wireworms. 


b.     Potatoes  eaten  by  white  grubs. 


PLATE  XVIII. 


a.     Adult    of   Stalk  Borer, 
natural  size. 


b.    Immature  Stalk  Borer  in 
corn,  natural  size. 


c.     Potato  Shoot  infested  with  Potato  Aphid,  natural  size. 


PLATE  XIX. 


a.     Infested  blossom  stems,  natural  size. 


b.     Aphids  on  the  under  side  of  the  leaves,  natural  size. 
POTATO  APHID. 


PLATE  XX. 


■ 

I 

^^ 

jfl 

H 

1 

a.     Parasitized  aphicls  on  upper  side  of  leaf,  natural  size. 


b.     Four-Lined  Leaf-Bug  and  its  injury  to  potatoes.     Leaves  reduced. 
Bug  about  natural  size. 


INSECTS   ATTACKING    POTATOES.     •  111 

are  by  no  means  confined  to  the  potato  but  may  include  nearly  any 
of  the  garden  vegetables  or  flowers. 

The  principal  species  are  the  black  blister  beetle  Epicauta  penn- 
sylvanica  Degeer,  the  margined  blister  beetle  E.  marginata  Fabr., 
the  striped  blister  beetle  E.  vittata  Fabr.  and  the  ash  gray  blister 
beetle  Macrohasis  unicolor  Kby.,  all  of  which  occur  in  great  num- 
bers in  certain  seasons,  and  all  of  which  occasionally  feed  upon 
potatoes.  These  beetles  are  common  on  flowers  of  golden  rod  in 
late  summer.    The  margined  blister  beetle  is  shown  on  plate  XVI,  b. 

The  larvae  of  blister  beetles  do  not  feed  upon  potato  foliage  like 
the  adults  but  as  they  devour  the  eggs  of  the  grasshopper  they  must 
be  regarded  as  beneficial. 

AVherever  blister  beetles  are  injuring  potato  plants  they  may  be 
controlled  like  any  other  leaf-eating  beetle — by  an  application  of 
lead  arsenate. 

The  Stalk  Bokek. 

Papaipema  nitela  Guen.,  and  other  species. 

Potato  stalks  are  often  noticed  which  have  been  tunnelled  up  and 
down  inside,  and  a  dirty  white  larva  strijDed  lengthwise  with  brown 
and  a  darker  saddle  about  one-third  of  its  length  from  the  head 
is  found  in  the  burrow.  This  is  commonlj^  known  as  the  stalk 
borer  and  is  supposed  to  be  Papaipema  nitela  Guen.,  but  there  are 
many  species,  and  several  new  ones  have  been  described  during  the 
past  few  years  by  Mr.  Henry  Bird  of  Eye,  N.  Y. 

Some  of  these  insects  are  restricted  in  their  food,  a  sjjecies  being 
found  only  in  one  kind  of  host  plant.  But  not  so  with  P.  nitela, 
which  attacks  many  different  kinds  of  plants,  including  most  of  the 
common  vegetables  and  field  crops,  and  many  of  the  flowers  and 
weeds.  In  fact  it  may  tunnel  in  almost  any  herbaceous  stem,  es- 
pecially those  of  larger  size.  It  is  often  a  serious  pest  of  tomatoes, 
potatoes,  corn,  dahlias,  lilies,  etc.  Corn  was  much  injured  by  it 
m  Connecticut  in  1918.  The  writer  has  often  found  it  in  rag^veed 
and  during  1918,  found  a  larva  boring  in  a  young  melon  plant  close 
to  the  ground. 

There  is  only  one  generation  each  year,  the  winter  being  passed 
as  a  pupa  in  the  soil.  The  adult  is  a  purplish-gray  moth  having  a 
wing-spread  of  about  one  and  one-fourth  inches.  A  common  form, 
var.  nehris,  has  the  fore  wings  marked  with  white  spots  as  shown 
on  plate  XVIII,  a.    The  lar^^a  is  about  one  and  one-half  inches  long 


112  CONNECTICUT   EXPERIMENT   STATION   BULLETIN    208. 

when  fully  grown,  and  has  the  appearance  shown  on  plate  XVIII,  b. 
No  control  measures  can  be  recommended  other  than  destroying  the 
infested  stalks  when  noticed. 

CUTWOEMS. 

Like  any  other  vegetables,  potato  plants  are  often  attacked  by 
cutworms  and  the  stems  eaten  off  near  the  ground.  Cutworms  are 
the  larvae  of  noctuid  moths,  and  there  are  several  species,  three  or 
four  perliaps  being  responsible  for  most  of  the  injury.  A  com- 
mon species  is  shown  in  figure  3.  There  is  one  generation  each 
year,  the  moths  emerging  and  the  eggs  being  laid  the  latter  part  of 
summer.  The  cutworms  become  partially  grown  before  winter 
then  go  deep  into  the  soil  to  remain  during  the  cold  weather.  Their 
native  food  consists  of  the  weeds  and  grasses.    In  the  spring  when 


Figure  3.     Black  cutworm  Agrotis  ypsilon.     (After  Howard,  Bureau  of 
Entomology,  U.  S.  Department  of  Agriculture.) 


warm  weather  comes  they  appear  to  be  hungry  after  their  long  fast, 
and  cannot  resist  attacking  the  tender  vegetable  plants. 

In  large  fields  where  cutworms  are  destructive  a  poisoned  and 
sweetened  mash  made  of  bran  should  be  employed.  The  follo\\dng 
formula  will  serve : 

Wheat  Bran    5  lbs. 

Paris  green  or  white  arsenic 5  ozs. 

Lemon  or   orange 1  fruit. 

Molasses    1  pint. 

Water   7  pints. 

Mix  the  dry  poison  and  bran  together.  Squeeze  the  juice  from 
thelemon  or  orange  into  the  water,  and  then  cut  the  pulp  and  peel 
into  fine  pieces  and  add  to  the  water :  then  add  molasses  and  stir. 
Mix  this  syrup  thoroughly  with  the  poisoned  bran.  This  will  make 
a  rather  dry  mash,  which  may  be  scattered  thinly  over  the  field  at 


INSECTS  ATTACKING  POTATOES.  113 

the  time  when  the  first  injury  is  noticed  or,  if  tobacco  or  tomatoes, 
a  few  days  before  the  plants  are  set.  If  applied  Just  before  dark, 
the  cutworms  will  have  a  chance  to  eat  it  before  it  dries,  the  citrus 
juice  and  molasses  attracting  them. 

If  it  is  feared  that  birds  or  poultry  will  partake  of  the  poison,  a 
spoonful  may  be  placed  in  a  hole,  here  and  there  and  covered  with 
a  stone,  or  a  bit  of  board. 

Late  fall  plowing  uncovers  many  cutworms,  thus  exposing  them 
to  birds  and  other  natural  enemies.  Extremely  thorough  harrow- 
ing will  kill  many  of  them. 

If  one  has  only  a  few  plants,  these  may  be  protected  by  wrapping 
the  stems  with  paper  or  cardboard. 

"WiEEWOEMS. 

Wireworms  are  the  larvae  of  "click"  or  "snap"  beetles  and  belong 
to  the  family  Elateridae.  There  are  several  species  which  injure 
cultivated  crops,  most  of  them  belonging  to  the  genera  Agriotes, 
Melanotus  and  Drasterius.  They  are  small,  hard,  cylindrical  lar- 
\ae,  and  are  usually  tan  or  reddish-brown  in  color.  They  are 
usually  more  troublesome  in  sod  land  and  first  bore  into  the  seed 
tubers,  then  tunnel  into  the  main  stem  of  the  plant  just  below  the 
surface  of  the  ground,  occasionally  causing  considerable  damage  in 
early  summer.  Later  in  the  season  they  tunnel  into  the  tubers, 
causing  the  injury  sho-\\Ti  on  plate  XVII,  a,  particularly  in  the 
"scabbed"  areas  greatly  injuring  the  appearance  and  market  value 
as  well  as  the  real  value  of  the  tubers  for  food.  From  three  to  five 
years  are  required  for  wireworms  to  go  through  their  complete  life 
cycle,  and  all  stages  except  the  adult  are  spent  in  the  soil.  They  are 
usually  more  abundant  and  therefore  more  troublesome  in  sod  land 
than  in  old  ground.  Crop  rotation  should  be  practiced.  Where 
possible  plow  sod  land  in  the  fall  and  harrow  at  frequent  intervals 
before  the  ground  freezes.  T\Tiere  wireworms  are  abundant  potatoes 
should  be  dug  as  soon  as  ripe  as  they  will  be  seriously  injured  if  al- 
lowed to  remain  for  several  weeks  in  the  ground. 

White  Gkubs. 

Like  wireAvorms  and  cutworms,  white  grubs  feed  naturally  in 
grass  lands  and  are  responsible  for  much  injury  to  crops, — es- 
pecially in  certain  seasons  and  when  planted  on  sod  land.  White 
grubs  are  the  larvae  of  the  May  or  June  beetles  belonging  to  the 


114  CONNECTICUT   EXPERIMENT   STATION   BULLETIN   208. 

genus  Lachnosterna  of  the  family  Scarabaeidae.  There  are  some 
fifteen  species  occurring  in  Connecticut,  but  as  Lachnosterna  fusca 
Froh.,  L.  crenulata  Forst.,  L.  liirticula  Ivnoch.,  L.  nova  Smith  and 
L.  fraterna  Harris,  are  some  of  the  commoner  kinds,  it  is  to  be 
supposed  that  they  are  responsible  for  the  damage. 

The  life  cycle  of  our  chief  species  requires  three  years  for  its 
completion.  The  eggs  are  laid  in  the  soil  at  a  depth  of  from  one  to 
eight  inches  late  in  May  or  early  in  June,  and  are  white  and  about 
one-tenth  of  an  inch  lodg.  The  young  grubs  feed  on  decaying 
vegetation  but  early  eat  the  roots  of  living  plants.  They  do  their 
greatest  damage  in  the  second  year  of  their  larval  existence,  but 
may  be  destructive  to  early  plantations  in  the  spring  of  their  third 
season. 


Figure  5.    June  beetle, 
Figure  4.    White  grub.  adult     of     white     grub. 

Natural  size.  Natural  size. 

Certain  seasons  are  remarkable  for  the  widespread  damage  caused 
by  white  grubs.  Thus  there  was  much  injury  in  Connecticut  in 
1915,  and  warnings  were  isuued  to  the  effect  that  grubs  might  be 
expected  in  1918.  As  a  matter  of  fact,  w'hite  grubs  were  reported 
as  doing  damage  in  a  few  localities  in  1918,  but  it  was  not  as  serious 
as  in  1915. 

Much  of  the  injury  is  done  to  grass  land,  but  when  infested  grass 
land  is  plowed  and  planted  to  potatoes,  the  grubs  will  often  cause 
serious  injury  to  the  crop  by  eating  o£E  the  roots  of  the  plants,  and 
also  eating  into  the  tubers. 

A  white  grub  is  sho'wn,  natural  size,  in  figure  4,  the  adult  beetle 
in  figure  5,  and  an  injured  potato  on  plate  XVII,  b. 

There  are  several  parasites  of  white  grubs,  including  wasps  of 
the  genera  Tipliia  and  Elis,  and  the  two-winged  flies  Pyrgota 
undata  Wied.,  P.  valida  Harr,  Promachus  fitchii  0.  S.  and  P.  verte- 
hratus  Say.    All  except  the  last  occur  in  Connecticut. 


INSECTS  ATTACKING  POTATOES.  115 

Of  the  many  vertebrates  destroying  white  grubs  and  their  adults, 
the  larger  birds,  farm  fowls,  and  skunks  are  probably  the  most  im- 
portant. 

Control  Measures:  Crop  rotation  is  one  of  the  methods  of 
forestalling  serious  injury  from  white  grubs.  Fall  plowing  of 
infested  land  before  October  10,  will  expose  many  of  the  grubs 
w'here  they  will  be  eaten  by  birds.  If  poultry  or  swine  can  be  turned 
upon  the  plowed  field  a  much  larger  proportion  of  the  grubs  will  be 
destroyed.  This  land  should  be  disked  and  harrowed  very  thor- 
oughly before  planting. 

If  potatoes  follow  clover  or  corn  in  a  white  grub  year  they  will 
not  be  greatly  damaged. 

As  has  already  been  advised  in  relation  to  wirewonns,  if  grubs 
are  abundant  or  troublesome,  the  potato  crop  should  be  dug  as 
soon  as  the  tubers  are  mature. 

SUCKIN"G  IIs^SECTS. 

Sucking  insects  do  not  tear  away,  masticate  and  devour  any  por- 
tion of  the  plant,  but  suck  out  the  plant  juices,  and  thus  obtain  their 
nourishment  in  liquid  form.  Each  insect,  therefore  is  fitted  with 
a  sucking  tuhe  known  as  rostrum  or  proboscis,  which  it  thrusts  into 
leaf  or  stem  and  through  it  sucks  out  the  sap. 

Insects  of  this  kind  cannot  be  controlled  with  arsenical  poisons, 
but  something  must  be  applied  that  will  kill  them  by  contact,  and 
nicotine  solution  and  oil  and  soap  emulsions  are  used  for  this  pur- 
pose. 

The  Potato  Aphid. 

Macrosiphum  solaiiifoUi  Aslim. 

Both  in  1917  and  1918,  this  aphid  caused  considerable  damage  in 
the  potato  fields  in  the  southern  half  of  the  state,  and  an  account 
of  the  former  infestation  was  published  in  the  Eeport  of  this 
Station  for  1917,  page  290.  This  aphid  is  often  called  the  pink  and 
green  potato  aphid  because  some  individuals  are  pink  or  reddish 
and  others  are  green.  It  is  shown  in  figure  6,  and  occurs  commonly 
on  solanaceous  plants  as  well  as  on  rose,  beet,  squash,  lettuce,  com, 
milkweed,  bitter-sweet  and  many  weeds  and  other  plants  around  the 
field.  During  the  past  18  years  it  has  been  collected  a  dozen  times  on 
several  difi'erent  plants  in  various  parts  of  the  State.  The  earliest 
record  is  June  18,  1901,  New  Haven,  on  Clematis  crispa.     Some  of 


116  CONNECTICUT   EXPERIMENT   STATION   BULLETIN   208. 

these  records  were  from  potato  and  tobacco,  but  the  insect  did  not 
cause  any  severe  or  wide-spread  injury  to  the  potato  crop  until  1917, 
when  it  damaged  fields  in  every  county  in  the  State,  and  was  re- 
ported from  many  localities  in  New  Haven  and  Hartford  Counties. 
The  vines  soon  died  and  the  crop  was  lig'ht  on  account  of  this  in- 
jury. In  1918,  the  writer  had  a  better  chance  to  observe  the  work 
of  this  aphid.  It  was  first  seen  at  the  Station  farm  at  Mt.  Carmel 
on  June  11,  a  very  few  individuals  (probably  stem  mothers)  here 
and  there  on  the  under  sides  of  the  leaves  in  the  northeast  corner  of 


Figure    6.     The    potato    aphid,   winged   female,    summer    form. 
Greatly  enlarged. 


tbe  field.  On  June  14,  they  were  more  abundant,  both  pink  and 
green  wingless  fomis  being  present,  and  some  had  begun  to  produce 
young. 

On  June  15,  Mr.  G.  M.  Codding  observed  that  potato  fields  in 
Greenwich  were  infested. 

On  June  20,  at  the  Station  farm  the  aphids  did  not  seem  to  be 
^ny  more  abundant  than  on  June  14,  but  a  week  later  (June  27) 
they  had  a,pparently  increased,  and  most  of  them  were  on  the  blos- 
som stems  as  shown  on  plate  XIX,  a.    A  few  occurred  underneath 


INSECTS  ATTACKING  POTATOES.  117 

the  new  leaves  at  the  top  of  the  plants.  It  seemed  advisable  to 
spray,  and  tests  were  first  made  with  a  number  of  promising  mate- 
rials which  were  thought  might  take  the  place  of  soap  without 
the  attending  danger  in  the  presence  of  lead  arsenate.  The  field 
was  sprayed  however,  July  2nd  and  3rd  with  nicotine  solution 
added  to  Bordeaux  Mixture  and  lead  arsenate,  using  one  pint  of 
Black  Leaf  No.  40  in  a  barrel  (50  gallons)  of  the  mixture.  The 
treatment  was  not  very  successful,  as  the  slight  wax  secretion  re- 
pelled the  spray  which  rolled  off  in  drops  leaving  many  of  the 
aphids  unliarmed.  Of  course  a  large  proportion  of  them  were 
killed.  In  three  weeks  aphids  again  became  so  aibundant  that  the 
field  was  sprayed  again  on  July  22  and  the  few  days  following.  By 
this  time  many  of  the  topmost  leaves  were  curled  and  the  aphids 
were  very  abundant.  ISTicotine  solution  had  been  in  great  demand, 
and  many  retail  dealers  had  sold  out.  A  fresh  supply  could  not  be 
obtained  from  the  factory  soon  enoug^h  to  save  the  crop.  Conse- 
quently we  demonstrated  that  kerosene  emulsion  would  answer 
the  purpose,  at  less  expense,  and  the  materials  could  be  purchased 
in  any  grocery  or  general  country  store.  The  following  quantities 
and  materials  were  used: 

FOEMULA. 

Laundry  soap   (about  30  oz.) 3  cakes. 

Kerosene    4  gals. 

Water    2     " 

After  churning,  dilute  eight  times  to  make  one  barrel  (50  gals.) 
~The  soap  was  cut  in  thin  slices  and  dissolved  in  hot  water  over  a 
fire.  It  was  then  removed  from  the  fire  and  added  to  the  kerosene, 
and  the  whole  churned  violently  for  a  few  minutes  by  passing 
through  a  bucket  pump  with  a  small  hose  directed  into  the  same  con- 
tainer. This  made  a  uniform,  creamy  mass,  from  which  the  oil  did 
not  separate  on  standing.  It  was  applied  with  strong  pressure, 
through  a  fine  nozzle  and  a  rod  bent  at  an  angle  of  about  45  degrees 
near  the  nozzle  by  means  of  which  it  was  possible  to  direct  the 
spray  against  the  under  surface  of  the  leaves. 

All  the  apliids  hit  by  the  spray  were  killed  without  injury  to  the 
plants.  They  disappeared  soon  after  and  no  further  treatment  was 
necessary. 

The  more  common  lady  beetles,  certain  syrphid  flies  and  lace- 
wings  feed  upon  the  aphids,  and  many  aphids  were  parasitized  by 


118  CONNECTICUT   EXPERIMENT   STATION    BULLETIN    208. 

a  small  four-winged  parasitic  fly,  Aphidius  rosae  Ilalliday,  as  shown 
on  plate  XX,  a. 

This  aphid  may  be  controlled  by  spraying  as  above  indicated,  but 
in  some  cases  it  is  practically  impossible  to  spray  the  under  side 
of  the  leaves.  Brushing  the  vines  just  before  cultivating  will  de- 
stroy a  large  proportion  of  them.  A  driving  rain  or  heavy  down 
pour  is  very  eflective  in  destroying  these  aphids  at  the  time  of 
their  maximum  abundance.  The  aphids  are  shown  on  the  blossom 
stems  and  on  the  leaves  on  plate  XIX,  also  parasitized  ones  on 
plate  XX,  a,  and  the  spraying  operations  on  plate  XIII,  b. 


The  Four-Lined  Leaf-Bug. 

Poecilocapsus  lineatus  Fabr. 

This  insect  is  generally  regarded  as  an  occasional  pest  of  small 
fruits  but  sometimes  also  injures  garden  vegetables  and  field  crops. 
In  1918,  the  writer  observed  several  instances  of  severe  injury  to 
certain  plants  usually  near  the  margin  of  tlie  field,  and  close  to  a 
woodland  or  weedy  uncultivated  field.  Injured  leaves  are 
shown  on  plate  XX,  b. 

The  four-lined  leaf-bug  lays  its  eggs  in  the  soft  tender  stems  of 
currant  and  doubtless  other  plants  about  the  first  of  July.  These 
eggs  are  long  and  slender,  someVhat  curved,  and  are  crowded  to- 
gether in  clusters  of  six  or  eight  and  are  pushed  end-wise  into  the 
soft  pith,  the  outer  ends  showing  as  a  patch  of  white. 

These  eggs  hatch  the  following  spring,  and  about  the  middle  of 
May  the  young  bugs  first  appear  on  the  top-most  and  tenderest 
leaves.  They  suck  out  the  green  pulp  from  the  under  side,  leaving 
roundish  semi-transparent  spots,  v^diich  often  coalesce.  As  the  in- 
sect increases  in  size  it  sucks  out  the  pulp  from  larger  areas,  and 
the  leaf  finally  turns  brown,  dries  up  and  dies.  This  injury  is 
characteristic,  but  the  insects  causing  it  hide  away  beneath  the 
leaves  and  are  seldom  noticed  unless  one  is  hunting  for  them. 

The  nymphs  at  first  are  brig'ht  red  marked  with  black  spots  but 
soon  change  to  bright  orange-yellow.  They  pass  through  five  stages 
in  about  three  weeks,  and  w'hen  mature  are  A\dnged,  nearly  one-third 
of  an  inch  long,  bright  greenish-yellow,  with  four  black  stripes 
running  lengthwise  on  thorax  and  wing-covers  as  shown  on  plate 
XX,  b. 


INSECTS  ATTACKING  POTATOES.  119 

Probably  the  best  control  measure  is  to  spray  thoroughly  the 
under  side  of  the  top  leaves  with  nicotine  solution,  two  teaspoon- 
fuls  in  one  gallon  of  water,  with  one-inch  cube  of  soap  dissolved  and 
added,  or  if  a  quantity  is  needed,  one  pint  of  nicotine  solution  and 
two  cakes  of  laundry  soap  in  50  gallons  of  water. 

Summary. 

The  potato  crop  in  Connecticut  is  injured  by  a  number  of  chew- 
ing insects,  the  most  important  being  the  Colorado  Potato  Beetle 
a.nd  the  Potato  Flea  Beetle.  The  Three-Lined  Potato  Beetle,  Tor- 
toise Beetles,  Blister  Beetles,  the  Stalk  Borer,  cutworms,  wire- 
worms  and  white  grubs  all  cause  occasional  damage.  All  but  the 
last  four  may  be  controlled  by  spraying  with  lead  arsenate.  Cut- 
worms may  be  destroyed  by  the  use  of  a  poisoned  and  sweetened 
bran  mash  scattered  about  the  field.  Against  wireworms  and  white 
grubs  cultural  practices  are  the  only  remedies. 

The  principal  sucking  insect  attacking  potatoes  in  Connecticut  is 
the  Potato  Aphid  which  can  be  killed  by  spraying  with  nicotine 
solution  and  soap,  or  with  kerosene  emulsion.  The  Four-Lined 
Leaf  Bug  causes  occasional  damage  and  may  be  controlled  by  the 
same  sprays  as  are  used  against  the  Potato  Aphid. 

Information  regarding  each  of  these  pests  and  the  measures 
necessary  to  control  them  may  be  found  in  the  foregoing  pages,  and 
most  of  them  are  shown  on  plates  XIII-XX. 


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